docs: def scroll_deck_x(self, decknum, scroll_x):
          """Move a deck left or right."""
          if decknum >= len(self.decks):
              raise IndexError("I have no deck at {}".format(decknum))
          if decknum >= len(self.deck_x_hint_offsets):
              self.deck_x_hint_offsets = list(self.deck_x_hint_offsets) + [0] * (
                  decknum - len(self.deck_x_hint_offsets) + 1
              )
          self.deck_x_hint_offsets[decknum] += scroll_x
          self._trigger_layout()